Tyrosinemia Type I is a lethal inherited inborn error of metabolism which produces cirrhosis of the liver and hepatocellular carcinoma. Until recently, the only effective therapy was liver transplant. The drug NTBC has been developed as an inhibitor of 4-hydroxyphenylpyruvate dioxygenase. The drug is well tolerated and produces dramatic biochemical improvement. Long-term studies of the drug to determine if it avoids cirrhosis and hepatocellular carcinoma are in process and the drug has been adopted by a pharmaceutical company. One patient is being studied at the University of Michigan.